An immobilized enzyme membrane fabrication method using an ink jet nozzle

Abstract

A novel enzyme immobilization method, which realized the efficient use of enzymes for biosensors, was developed. An ink jet nozzle, originally developed for printing equipment, was used as a tool for precise enzyme deposition onto an ISFET device. Two sorts of immobilization method were attempted: one is liquid phase immobilization, in which an enzyme solution was emitted at first onto an ISFET sensor region. After drying it under room temperature, glutaraldehyde solution was emitted into the enzyme membrane for immobilization. In this method, the membrane became very thin (e.g. less than 0.1 μm) in a region around the center. In addition, membrane thickness control was rather difficult because the enzyme solution redissolved into the glutaraldehyde solution, and membrane localization at the peripheral region occurred. Next, the method was improved so as to maintain the shape of the original enzyme drops: gas phase immobilization. At first, enzyme solution drops were emitted onto an ISFET device whose position was precisely determined using an X-Y stage controlled by a personal computer. Enzyme immobilization was realized by keeping the device in a chamber filled with glutaraldehyde vapor. In this case, the resulting membrane shape maintains the original enzyme shape. These methods will have great merit in very expensive enzyme immobilization and in the fabrication of a multi-biosensor, which has various kinds of immobilized enzyme membranes on a sensor chip.